Process for producing copying paper



Patented Apr. 14, 1942 Rudolf Wiilti, Basel, Switzerland.

No Drawing. Application September 7, 1937, Se-

iigllsNo. 162,764. In Germany September 16,

1 Claim.

The object of my invention is the production of a liquid copying composition to be applied in the form of a thin and smudge-proof coat to the.

surfaces of writing or drawing papers, in par-1 ticular typewriting papers, as an improved substitute for the commonly used carbon paper.

Ihave found that I was able to eliminate the various inadequacies and disadvantages inherent in and connected with the manufacture and use of the common carbon paper by substituting for the waxy-oily or fatty dye-paste coating of the latter aqueous solutions or emulsions of substances forming elastic films, such as, e. g., liquid latex. Since I apply or spread on the dye-carrying paste in the cold state and since the latter,

tion or emulsion according to my present invenaside from the film-producing component and v the dye, contains only water, the ordinary ap- Paratus used for dyeing the paper also may be employed for the purpose of applying this dyecarrying paste. Such a latter coat, vapplied in a combination withsuch substances as, e. g., latex,

' onto a second sheet, may be applied now directly onto the back of the original writing sheet. The latter, therefore, is taking the place of the carbon paper heretofore inserted between the writing and the copying sheets.

A process has been known for some time, viz.

'the so -called Transcrit"-process, which also operates without the use of carbon paper. This process, mostly used only for the local printing on of the copyin dye-coat, is employing. however, the very same and relatively expensive dyefilm of the carbon paper, 1. e. a dye containing one therefore also has to "apply a thin coat of a film-producing substance to the surface of the sheet to be copied on.

It yet may be mentioned that by means of the writing and copying paper treated with the solution there may be made justas many copies as by means of the ordinary carbon paper usedheretofore.

Paper treated in accordance with the present invention, such as, e. g., coated with a solution of latex, may be written and printed on like any ordinary P per treated with glue. The process, therefore, also may be made use of ili' making forms to be copied either by hand or by means of the typewriter. a

The process is, e. g., applied as follows: The one side of a roll orsheet of paper first is impregnated with a solution containing, per litre, 20 grams of Revertex T (a latex-concentrate containing about 75% dry substance) to which, if need be and so desired, protective agents against a e. g. phenyl-betanaphtylamin,- are added.

After impregnating the sheet is dried, and the dye-paste is applied to the back of the sheet.

to app y the one or the other of the latter coats only in certain places instead of over the entire surface of the paper. For'this latter operation one suitably adds a thickening agent to the latexsolutions such as, e. g., glue. Dyes preferably to be used are: carbon black, mineral colors appear- -ing on the market under the name of Ultramawaxes, oils or fats as binding agents. For applying such a. latter coat, furthermore, a set of special and relatively complicated machines is required which are eliminated in the process according to the present invention.

A further pronounced difierence between the' present and the known processes is that the paper of the former has to be coated on both sides. The dye on the back of the sheet, bound by the sulfonates etc. known to the trade under the film-producing substance such as, e. g., latex,

does not copy onto ordinary copying paper; which, by the way, also is the effect of its smudge-proofness, since the said dye cannot be rine, Hansa-colors, Vulkan-colors and the like which are free from manganese and copper and which do not precipitate the caoutchouc. Adding a dispersing agent (sulfonation-products of fats and condensed aromatic solvents, fat-alcohol names Melioran, Igepon T, Peregal 0 and so on) has 'proven of excellent value for .finely dis-. tributing the dyes in the aqueous-solution.

In preparing the dye-paste composition I pre-' fer, by way of example, to use the ingredients in about the following proportions and to add them in the following mannerviz., grams of carbon black, cc. of water and 40 grams of a 10% I epon T solution are made into 'a. paste and, by stirring, added to a. solution of 40 grams Revertex T in 760 cc. of water. The quantity obtained readily rubbed oil. In order to obtain a copy, 55 thenis 1 kilogram. To this dye-paste also, in

I gluing operation.

any given case, a protective meansragainst aging may be added.

The quantities of carbon black and Revertex T given in the above example obviously may be increased or decreased according to requirements. One also may proceed by first coating the paper with the dye-paste and .then applying the 2% Revertex T solution.

A variation of the process described consists in .using unglued paper, substituting the passing of the paper through a Revertex-solution for the After such a passage the coat is dried and then the dye-film spread on.

An exampl for the Revertex-solution used is as iollows: To 60 grams of Revertex 940 cc. of water are slowly added, the quantity obtained is 1 kilogram.

- prising coating one side of said paper with an aqueous dispersion of latex and then coating the other side of said paper with an aqueous dispersion of latex and a coloring substance tree from a precipitating action upon said latex.

RUDOLF WKLTI. 

